ADDEO, NICOLA FRANCESCO (2021) Insects: the new challenge of animal farming for a more sustainable feed and food production. [Tesi di dottorato]

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Population growth and rapid urbanization have increased the global demand for animal feed and protein sources. Therefore, the traditional production of animal feed should be increased through the use of alternative nutrient sources. Insects as feed are starting to meet this need. One such insect is the black soldier fly, Hermetia illucens L. (Diptera: Stratiomyidae). However, in order to mass- produce the black soldier's fly (BSF) more effectively, a better understanding of its thermal biology is needed. Therefore, the aim of one of the five contributions of this thesis was to evaluate the impact of age, size and sex on thermal preference for adult black soldier flies. The thermal preference of adult black soldier flies was determined by exposing the flies to a thermal gradient with a range of surface temperatures and monitoring their location over time. An aluminum plate was used to create a linear thermal gradient in which surface temperatures ranged from 15 to 60 ° C. The flies were distinguished by age (1 day after emergence vs 7 days after emergence), size (large vs small) and gender (male vs female) to assess whether thermal preference differed from specific life history traits. Thermal preference for 7- day post-emergence adults was significantly lower (19.2 ° C) than for 1-day post-emergence adults (28.7 ° C), respectively. Similarly, small adults selected significantly cooler temperatures (21.1 ° C) than large adults (26.9 ° C). There were no significant differences in thermal preferences between the sexes, regardless of age or size. Indeed, males and females had a similar thermal preference of 23.8 ° C and 24.2 ° C, respectively. Due to the high sustainability of insect farming, the possibility of breeding insects as a food and feed source appears to be very promising. Reusing and enhancing food waste is possible by using it as a substrate for the growth of insects. In this context, BSF can grow on a wide range of substrates turning it into valuable biomass. In the second contribution, four different substrates were used and evaluated for their suitability for the reproduction of the larvae. Hermetia illucens larvae (five days old) were raised on chicken feed (control diet), a vegetable diet (V100), a 50% vegetable diet + 50% butchery waste (V50 + B50) and a vegetable diet 75% + 25% of butchery waste (V75 + B25) to assess their suitability. Ten kg of substrate and 6,000 larvae made up each replicate (9 per group). The larvae were weighed and measured every two days until 25% developed into prepupae. Mortality and larval growth rates were calculated. Ash substrates, larvae and chemical composition were analyzed. The oxidative state and stability of the larvae were measured in the hemolymph and in the body. V100 larvae exhibited the lowest live weight, length, thickness, and growth rate, but had a low mortality rate, high substrate reduction rate, and protein conversion ratio. The V100 larvae had similar proteins and lower lipids than the control ones while the V50 + B50 and V75 + B25 larvae contained higher lipids and lower proteins than the others. Although plant wastes, to varying degrees, reduced the reactive oxygen species content of the hemolymph, the V100 diet reduced growth performance and should be avoided. Butchery waste may be suitable, but it must be well combined with other ingredients to balance the high lipid level and low protein content, and vegetable waste may be an appropriate candidate. Vegetable and butchery waste is easy to find and collect and, in the present study, showed interesting potential for BSF larvae growth by producing insects with interesting chemical characteristics at 22 days of age. The use of plant waste reduced the level of reactive oxygen species in the insects' hemolymph, suggesting a positive effect on the welfare of the larvae. In recent years, several studies have focused on the use of insect larvae meal as an alternative to soybean meal in poultry diets. In this regard, it is essential to try to understand all the possible aspects related to the chemical-nutritional characteristics, the effects on animal health and welfare, and the impact on food safety of the various insect flours. Another contribution of this project aimed to evaluate the production of volatile fatty acids in the caecum, the intestinal morphometry and the enzyme activity of the brush rim of hens fed with increasing levels of Hermetia illucens maggot meal. To evaluate the effects of feeding a Hermetia illucens (HI) larvae meal on different intestinal tracts of hens and to determine the concentration of trace and toxic elements in insect meal and diets, 162 hens were divided into three age groups between 16 and 40 weeks. The control was fed a cornmeal and soybean meal (SBM) diet; the HI25 and HI50 groups were fed two diets in which 25% and 50% of the dietary protein were replaced by the HI protein, respectively. The height of duodenal and jejunal villi and villi / crypt were higher (P <0.01) in the SBM than in the HI groups. Ileal villus height was greater (P <0.05) in the SBM and HI25 groups compared to HI50. The HI50 group had inferior duodenal maltase activity. IAP decreased linearly in the duodenum and jejunum with increasing inclusion of the insect meal in the diet. Ileal -GT activity was greater in SBM than in both insect groups (P <0.05). The HI50 group had higher acetate and butyrate than SBM, with potential positive effects on gut health. Levels of toxic elements such as Cd, Pb, Hg, and as in diets and insect meal were lower than the maximum levels of heavy metals set by the EU Commission for feed. The forth contribution, conducted for this PhD project, was done on a total of 120 Japanese 12- week-old quail females, who were divided into 4 groups (6 replicas of 5 birds each). The control group (CON) fed a corn and soy diet; in the other 3 groups, Tenebrio molitor grub meal (TML) replaced 5, 10 and 20% of the soy protein (T5, T10 and T20). Spawning performance and egg quality were studied for 54 days. The data was processed by a one-way ANOVA; Orthogonal contrast analysis was performed to test linear, quadratic, and cubic effects between the means. Egg-laying rate and egg mass decreased linearly (P <0.01) as the level of inclusion of TML in the diet increased. Egg weight and feed conversion ratio increased linearly from control to T20 diet (P <0.01) while digestibility of dry matter, organic matter and crude protein decreased linearly (P <0.05). Egg white and yolk weight showed a linear increase (P <0.01) due to the inclusion of TML in the diet, while eggshell weight showed the opposite (P <0.05). Estimated Δ9-desaturase (C16: 0), 5 + Δ6-desaturase activity on both n-6 and n-3 polyunsaturated fatty acids increased linearly (P <0.05) as influenced by dietary LMT. The lightness of the boiled yolk (L *) showed higher values in the T5 and T10 groups (quadratic contrast, P <0.01). The yolk redness index (a *) showed lower values in T5 and T20 compared to the control and T10 groups (cubic contrast, P <0.01). The albumen indices L *, a * and b * showed a significant quadratic contrast effect (P <0.05). Furthermore, the albumen index b * showed a significant effect of the cubic contrast (P <0.01). Total lipids showed the highest values (cubic contrast, P <0.05) in the T10 and T20 groups. Total monounsaturated fatty acids increased linearly (P <0.05) based on the increase in dietary LMT. The best inclusion level of the TML defatted meal for laying quail appears to be 1.4% of the diet, corresponding to the T5 diet. The latest contribution of this PhD project was aimed at proposing the larvae of the queen of honeybees, discarded from the production of royal jelly, as a possible food supplement in animal nutrition. To this end, the chemical characteristics, chitin content, amino acids, fatty acids and mineral profile (including toxic elements) were determined on pooled samples of queen bee larvae. Queen bee larvae meal is rich in chitin, proteins, essential amino acids and some essential minerals such as phosphorus and magnesium; it is also relatively low in fat, and with negligible levels of toxic elements such as Cd, Pb, As and Hg. However, its fatty acid profile showed a very low amount of polyunsaturated fatty acids and the flour was low in Ca and other trace elements compared to the more common insect flours used in feed. Queen bee larvae have a standard royal jelly diet and this could be a great advantage for use in animal production. However, the collection of the queen bee larvae does not allow to give high quantities of final product both for the low quantity of collected larvae (on average 58.9 g / hive / month) and for the relatively low yield of flour (on average 23, 12%) registered. Therefore, queen bee larvae meal cannot be considered an alternative protein source in animal production but could represent a potential dietary supplement to be inserted at low doses to exploit the possible modulating activities of the intestinal microbiota due to the high levels of chitin. The use of insects for feeding farmed animals represents a promising alternative because of the nutritional properties of insects and the possible environmental benefits, given the sustainability of this type of farming. Although rapid development is expected, insects remain underutilized in the animal feed industry mainly due to technical, financial, and regulatory barriers.

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